On 1/11/07, Nick Piggin <nickpiggin@yahoo.com.au> wrote:> Andrew Morton wrote:> > On Thu, 11 Jan 2007 14:45:12 +0800> > Aubrey <aubreylee@gmail.com> wrote:> >> >> >>>In the interim you could do the old "echo 3 > /proc/sys/vm/drop_caches"> >>>thing, but that's terribly crude - drop_caches is really only for debugging> >>>and benchmarking.> >>>> >>> >>Yes. This method can drop caches, but will fragment memory.> >> >> > That's what page reclaim will do as well.> >> > What you want is Mel's antifragmentation work, or lumpy reclaim.> >> >> >>This is> >>not what I want. I want cache is limited to a tunable value of the> >>whole memory. For example, if total memory is 128M, is there a way to> >>trigger reclaim when cache size > 16M?> >> >> > If there was, it'd "fragment memory" as well.> >> > You might get a little benefit from increasing /proc/sys/vm/min_free_kbytes,> > but not much. Some page allocation tweaks would aid that.> >> > But basically, to do this well, serious work is needed.>> OTOH, the antifragmentation stuff can also break down eventually,> especially if higher order allocations are actually in common use.

That's right. When VFS cache eat up almost all of the memory, I thinkno memory algorithm can help the case, including Mei's anti-fragmentpatch.

>> What you _really_ want to do is avoid large mallocs after boot, or use> a CPU with an mmu. I don't think nommu linux was ever intended to be a> simple drop in replacement for a normal unix kernel.

Is there a position available working on mmu CPU? Joking, :)Yes, some problems are serious on nommu linux. But I think we shouldtry to fix them not avoid them.